In assisted reproductive technology (ART), pregnancy and birth rates following in vitro fertilization (IVF) attempts remain low. Indeed, 2 out of 3 IVF cycles fail to result in pregnancy (SART 2004) and more than 8 out of 10 transferred embryos fail to implant (Kovalevsky and Patrizio, 2005). In addition, more than 50% of IVF-born babies are from multiple gestations (Reddy et al., 2007). Preterm deliveries that result from multiple pregnancies caused by ART are estimated to account for approximately $890 million of U.S. health care costs annually (Bromer and Seli, 2008).
The selection of embryos with higher implantation potential has been one of the major challenges in ART. This selection is currently based on morphological criteria such as growth rate, early cleavage on day-1, degree of fragmentation and blastocyst formation (Ebner et al., 2003). However, the predictive power of this approach is still limited. With the emergence of new technologies like ‘omics’, there are new biomarkers as discovery tools that can be applied to IVF for oocyte and/or embryo selection (Hillier, 2008).
Legal and ethical considerations make biomarkers directly directed to oocytes or embryos difficult to implement. Thus, to avoid any invasive method, some studies have been focused on cumulus cells (CCs).
Indeed, transcriptomic approaches using microarray technology, allowing the simultaneous screening of thousands of genes, were intensively used to identify in CCs the biomarkers related to oocyte competence, which is defined as the intrinsic ability of oocytes to undergo meiotic maturation, fertilization and embryonic development (McKenzie et al., 2004; van Montfoort et al., 2008).
Using the same approach, genes expressed in CCs used as biomarkers associated with embryo quality (McKenzie et al., 2004; van Montfoort et al., 2008; Zhang et al., 2005) and pregnancy outcome (Assou et al., 2008; Hamel et al., 2008; Hamel et al., 2010; Assou et al. 2010) have also been identified.
Even if these studies target the gene expression profile of CCs, a source of cells reflecting the biology and competence of both oocytes and embryos, there is a need to investigate further to develop a non-invasive method of predicting IVF outcome easier to use and with higher reliability.